The present invention relates to the feeding of welding wire electrode from a drum package to a welding gun.
A typical welding system utilizing a welding gun includes a source of welding wire arranged, for example, in spools, reels, or drums, and a feed mechanism which includes a pair of drive rolls for feeding the welding wire to the welding gun. Certain types of welding guns require that the welding wire maintain constant contact with a contact tip disposed at a discharge end of the welding gun. Otherwise, the welding wire becomes fed without being melted and, upon abutting against the workpiece, causes a tangling of the welding wire to occur at the feed rollers. This condition is known in the industry as bird nesting. In certain automated welding systems, a loss of contact between the welding wire and the contact tip can cause the system to shut down, resulting in a rejected unit or a unit requiring rework.
Loss of contact between the welding wire and the contact tip can occur, for example in straight-necked welding guns where a welding wire that has little or no inherent curvature may pass coaxially through the outlet of the welding gun without making contact with the tip. This problem does not occur in cases where the welding wire is extracted from a spool on which the wire is wound, because wire extracted from spools has an inherent curvature and thus will exit the welding gun in contact with a side (i.e., electrode) of the outlet. That is, a wire with curvature is physically incapable of exiting the outlet in coaxial relationship therewith. In cases where the wire is stored in a cylindrical barrel (drum), however, the wire has little or no inherent curvature, and a loss of contact with the electrode of a straight-neck welding gun can occur.
On the other hand, much more wire can be stored in barrels, than on spools, so a welding system using barrel-stored welding wire can operate for much longer periods before the system must be shut down to replace the welding wire.
Therefore, it would be desirable to enable welding wire to be supplied from a barrel without a risk that the welding wire will lose contact with a contact tip located at the outlet of a welding gun, such as a straight-neck welding gun.
Another problem can occur in welding operations utilizing a robotic welding gun which is subjected to a type of movement which causes a twist to be created in the welding wire. That twist can be transmitted back to the source of welding wire, such as a barrel, causing the welding wire to become knotted within the barrel.
Therefore, it would also be desirable to prevent a twist from being transmitted through the welding wire all the way to the source of welding wire.